The invention relates to an apparatus for thermal spraying.
Thermal spraying plays an integral role both in the coating of individual parts and in industrial mass production. Increasingly, coating plants are being used, in particular when surfaces of complex shape have to be coated in large volumes, in which program-controlled robots fully automatically guide a spray gun according to a predetermined movement program and thus take over the coating of the surfaces of the most varied components. As a rule, such plants have a supply unit which makes available the electrical energy, operating gases such as oxygen, nitrogen, inert gases or other gases, as well as cooling water and many other operating media required for the operation of the spray gun. The spray gun is then connected to the supply unit via a supply line, with the supply line then including, in dependence on the demand, corresponding electrical lines, cooling lines, gas delivery pipes, etc.
In special cases, sensors are additionally provided in or at the spray gun, or at the robot unit for example, to monitor the spraying procedure, or control element; or regulating elements such as temperature sensors, flowmeters, stepper motors or hydraulic or pneumatic control units and/or regulating units are provided which likewise have to be connected either to the supply unit or to further control units via corresponding supply lines.
The spray apparatuses previously explained schematically can be equipped with very different types of spray guns depending on which spray method should be used. For instance, different types of plasma burners can be provided, e.g. the Sulzer Metco plasma burner of the Triplex II type, an F4-MB plasma spray gun, a plasma spray gun of the 9 MB or 3 MB type or an “internal” plasma spray gun of the SM-F300 or SM-F100 Connex type which is particularly suited for the coating of internal surfaces such as cylinder bores, or also burners of other manufacturers such as the F6 burner of GTV.
However, not only plasma spray guns are used. The previously described apparatuses for thermal spraying can also be equipped, among other things, with spray guns for flame spraying with wires or powder, guns for flame shock spraying or high velocity flame spraying (HVOF) or with spray guns for arc spraying. This list of the possible types of spray guns is by no means exclusive. All possible types of spray guns can rather advantageously be used in such plants.
The specific selection of the spray method depends on different factors. Among other things, it depends on the type of the base material of the workpiece that should be coated. It also depends on the type of the material to be sprayed on or on the required functions for the coating to be sprayed (e.g. corrosion-resistant coating, heat-insulating coating, decorative coating, coating against mechanical wear, coatings with good tribological properties, protective coating against chemical influences, etc.). One or the other spray processes will provide special advantages in dependence thereon.
It is also not uncommon, for instance, for a workpiece to have to be provided, for example, with a plurality of coatings of different types lying above one another or next to one another which have to consist, for example, of different materials and/or have to be sprayed according to different processes, since the surfaces sprayed according to different processes can even have different properties when identical spray materials are used.
The different spray processes and the spray guns used therefor have long been very well known in the prior art and therefore do not need to be discussed more closely in detail at this point. A very exhaustive overview of spray processes and corresponding spraying apparatuses or spray guns is given, for example, in K. Smolka “Thermisches Spritzen, Ein Leiffaden für den Praktiker” [Thermal Spraying, A Guideline for the Practical User], Deutscher Verlag für Schweisstechnik, 1985.
Although, as already mentioned, the described apparatuses for thermal spraying with components such as robots for the guiding of the spray guns, supply devices for the supply of the spray guns with operating media (within the framework of this application, the term operating media should be understood to include everything which is required for the proper operation of a spray gun, that is, in addition to operating gases, spray powders or spray wires, also coolants, such as cooling water, or electrical energy or whatever operating media is required for the operation of the spray gun) or control units and regulating units have been well-known for a long time and are also solidly established in series and mass production, the change of the spray gun or of the burner of the spray gun has previously been very complex since, on the change of the spray gun or of the burner, the supply line, which frequently consists of a plurality of components such as an electrical feed line, a cooling water feed line, a supply line for operating gases, etc., has to be dismantled in a time-consuming manner.
In particular the burner hoses, e.g. with plasma burners, which, as a rule, are designed as internally cooled electrical supply lines, create problems here. On the one hand, the high electrical operating currents (typically approx. 500 A-700 A at 40 V-60 V operating voltage) have to be transported safely, that is, in particular free of flash-over and with good insulation, to the plasma burner and, on the other hand, the live internally cooled lines have to be sealed sufficiently against the cooling water standing under relatively high pressure (the water pressure in the line can easily amount to 16 bar and more). In addition, operating gases, in particular also inert gases, very frequently have to be supplied under more or less high pressure.
In the known apparatuses for thermal spraying, all these supply lines are therefore connected to the spray gun individually using different connectors, with different sealing devices, etc. The consequence is that the different supply lines have to be dismantled and reconnected again in a very time-consuming manner and using various tools when changing the spray guns or when replacing the supply unit which make the different operating media available.
A further problem consists of the known apparatuses for thermal spraying being very inflexible with respect to the types of spray guns and/or supply devices which can be used so that always only one and the same spray gun type can be used without complex conversion work in a given supply unit, since the corresponding connectors with seals, etc. differ according to the spray gun and/or supply unit used so that the connectors of the supply lines do not fit to one another at the interfaces between the supply unit and the spray gun.
This is, for example, particularly problematic when the spray gun has to be replaced frequently, for example for servicing purposes, or if different coatings have to be applied sequentially onto one and the same workpiece using very different spray methods. If, for example, a first coating is to be applied to a workpiece by means of a Triplex burner (Sulzer Metco) and a second coating is to be sprayed onto it using an F6 burner by GTV by means of plasma spraying, either two apparatuses for thermal spraying have to be provided and the workpiece has to be converted for the further coating in the plasma spray apparatus after the coating using the Triplex burner, or the Triplex burner has to be replaced by an F6 plasma spray gun, which is frequently either not possible at all or has to be effected with a huge effort of conversion measures which cannot be justified.